The invention relates to a multicylinder fuel injection internal combustion engine equipped with exhaust gas recycling. Particularly, the invention relates to an air guide casing for collecting a mixture of recycled exhaust gas and filtered intake air and distributing that mixture to the cylinders of the engine for combustion.
It is known to feed recycled exhaust gas into a current of air for combustion in order to achieve a better quality of exhaust gas in multicylinder internal combustion engines under certain operating conditions. German Unexamined Published Application (DE-OS) No. 29 47 940 discloses a system comprising an exhaust gas recycling pipe connected to the air inlet pipe at a point downstream of an air throttle valve leading to the internal combustion engine. The exhaust gas recycling pipe contains an exhaust gas recycling valve for controlling the exhaust gases.
In addition, it is known from German Unexamined Published Application (DE-OS) No. 28 51 180 to provide an exhaust gas recycling pipe leading into the air inlet pipe at a position downstream of an air throttle valve. The air inlet pipe conducts the air for combustion after such air has been treated by an air filter. An exhaust gas recycling valve is mounted in the air inlet pipe to regulate the flow of recycled exhaust gas thereinto.
The arrangement according to German Unexamined Published Application (DE-OS) No. 28 51 180 contains an air inlet pipe having an air filter disposed in an air guide casing, an air throttle valve, and an exhaust gas recycling valve. The exhaust gas recycling valve is situated in the air inlet pipe to be downstream of the air throttle valve. The air inlet pipe is an ordinary flow duct. A short mixing section lies between the recycling valve and the induction branch pipes leading to the individual cylinders of the internal combustion engine. This short mixing section is not sufficient for obtaining an almost homogeneous mixture of air and exhaust gas. Good distribution of the mixture to the individual cylinders is not achieved with the pipe arrangement used here.
One object of the present invention is to provide an air inlet pipe of compact contruction for a multicylinder internal combustion engine which will permit good mixing of the exhaust gas with the air for combustion and permit uniform distribution of the mixture of exhaust gas and air to the individual engine cylinders.
According to the present invention, a box-shaped air guide casing includes an air filter, an air throttle valve, a mixing section or chamber, and a distributor space or chamber. An exhaust gas recycling valve is disposed in an exhaust gas recycling pipe. The present invention provides a separate mixing section in the air guide casing to achieve good mixing of the air for combustion with the incoming exhaust gas prior to introduction of the exhaust gas and clean air into the distributor chamber. This novel feature advantageously causes an almost homogeneous mixture of air and exhaust gas to be uniformly distributed to the individual cylinders of the internal combustion engine. Furthermore, through the separation of the clean air side of the air guide casing from the mixing section and the distributor space, the air filter is protected against excessively high exhaust gas temperatures, while the soiling of the air filter by the exhaust gases is substantially reduced.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, an embodiment in accordance with the present invention.